A 45-year-old man undergoes elective tracheostomy for laryngeal stenosis. Postoperatively, he develops acute bleeding from the stoma on postoperative day 5. A 62-year-old woman with a chronic tracheostomy (placed 2 years ago for COPD) presents with persistent purulent drainage and granulation tissue at the stoma margins. Which finding best distinguishes early tracheostomy hemorrhage from chronic tracheostomy infection/granulation?